The invention is directed to a process to prepare a gas mixture of hydrogen and carbon monoxide from an ash containing carbonaceous feedstock.
Such a process is described in U.S. Pat. No. 4,474,584. In this process a coal is subjected to a partial oxidation. A mixture of liquid ash, solids and hydrogen and carbon monoxide is quenched with water and subsequently passed through a diptube into a bath of liquid water. The gaseous components and some solids are subsequently passed via a venturi mixer to a scrubber vessel. The ash particles in the water which leave the scrubber are removed in a hydrocyclone. The cleaned water is subsequently used as quench water.
A disadvantage of this process is that three types of water effluents are produced, namely a water stream from the hydrocyclone rich in solid ash, a water stream rich in solid ash as disposed from the water bath and a water stream less rich in solids as discharged from the same water bath. The number of effluent streams introduce complexity to the water treatment system. There exists a desire to simplify this process.
A further concern with the prior art process is that it does not disclose an efficient re-use of water. Especially in processes, which consume water, like coal to liquids (CTL) processes, re-use of water is important to minimize the consumption of water. Water is required to provide the hydrogen in a coal to liquids process involving partial oxidation of coal, a water gas shift process step and a Fischer-Tropsch process step.